Coal is the most abundant fossil fuel source available in the United States. In the early 1900s, before the rapid rise in energy demand for transportation, coal provided almost all the energy consumed in the US. In 1950 coal supplied approximately 36% of the total energy consumed, with petroleum and natural gas supplying most of the rest. Coal use increased steadily up until its peak in the mid-2000s when it supplied approximately 23% of total energy. Since then, its use has dropped rather dramatically, and as of 2018 supplied only 13% of the total. In terms of electricity alone, coal use for power has declined about 33% in 3 years. Such a dramatic decline has had an impact on US power infrastructure. Per the EIA, between 2010 and the first quarter of 2019, US power companies announced the retirement of more than 546 coal-fired units, totaling about 102 GW of capacity, with another 17 GW planned for retirement by 2025.
Historically, burning of coal has a number of significant negative consequences that have contributed to its decline as a source for power in the US:
Emissions of sulfur dioxide (SO2) and nitrous oxide (NOx), which cause acid rain and contribute to smog. Federal action to control air emissions from all major sources began in earnest with the 1970 Clean Air Act. However, SO2 and NOx emissions began to decline significantly after enactment of the 1990 Clean Air Act Amendments, which established a national cap-and-trade program for SO2 and required other controls for NOx emissions from fossil-fueled electric power plants. See OWOE topic How are air emissions from burning coal to generate electricity controlled?
Particulate emissions, such as soot and ash, which cause breathing issues and asthma, and heavy metals emissions, such as mercury, arsenic, and chromium, which have a wide range of health and environmental impacts. The EPA has issued several rules and standards to control particulate pollution that are achievable using existing pollution control technologies.
Large quatities of ash that is left behind after the coal is burned, which must be disposed of or stored. Although there are numerous approaches to managing ash, some are more environmentally friendly than others, and there have been recent serious incidents that have raised public awareness.
And, finally, carbon dioxide (CO2) emissions, which is the primary contributor to global warming. Although the scientific community is virtually unanimous on the correlation between CO2 levels in the atmosphere and global warming, and burning coal emits approximately twice as much CO2 as natural gas for the same heating value, there is strong corporate and political opposition to instituting any such rules. The problem is that there is no technically proven and economic way at this time to reduce carbon dioxide emissions caused by burning fossil fuels. See OWOE topic What is clean coal?
Although all of these issues can be addressed to the extent that they comply with current rules and regulations, there is a strong and growing movement in the country against coal. And while environmental issues typically frame the political debate over the future of coal power, cost is the primary driver to the recent decline in coal use in the US. In particular, low cost natural gas arising from the shale gas boom that began in the mid 2000s has resulted in new natural gas powered plants being cheaper in many cases than running an old coal plant. In addition, with the recent rapid cost decline of wind and solar, these renewable energy sources are now cheaper in some parts of the country. A March 2019 report by Energy Innovation concluded that "America has officially entered the 'coal cost crossover'...Today, local wind and solar could replace approximately 74 percent of the U.S. coal fleet at an immediate savings to customers. By 2025, this number grows to 86 percent of the coal fleet".
This report suggests a sunset scenario for coal power, with a likely steady flow of plant closures. If we accept the 86% number at face value, only about 37 GW of coal plant capacity (out of the 264 GW capacity in 2018) will remain in 2025. However, the report points out that there are monopoly utilities that support uneconomic coal generation at the expense of new renewables that will extend that date. Regardless, the end of the coal era in the US is much closer than anyone envisioned ten years ago.
The Coal Power Topics package provides information on a variety of coal power topics of general interest to the American public. Key references are provided that can be used to find more detailed information.